全文获取类型
收费全文 | 225478篇 |
免费 | 5770篇 |
国内免费 | 3732篇 |
专业分类
化学 | 127687篇 |
晶体学 | 3569篇 |
力学 | 9487篇 |
综合类 | 240篇 |
数学 | 23316篇 |
物理学 | 70681篇 |
出版年
2022年 | 1825篇 |
2021年 | 2200篇 |
2020年 | 2510篇 |
2019年 | 2629篇 |
2018年 | 2995篇 |
2017年 | 2989篇 |
2016年 | 4505篇 |
2015年 | 3136篇 |
2014年 | 4356篇 |
2013年 | 9828篇 |
2012年 | 8380篇 |
2011年 | 9910篇 |
2010年 | 6977篇 |
2009年 | 6750篇 |
2008年 | 8646篇 |
2007年 | 8390篇 |
2006年 | 8139篇 |
2005年 | 7525篇 |
2004年 | 6617篇 |
2003年 | 5972篇 |
2002年 | 5913篇 |
2001年 | 6322篇 |
2000年 | 4761篇 |
1999年 | 3916篇 |
1998年 | 3411篇 |
1997年 | 3281篇 |
1996年 | 3096篇 |
1995年 | 2919篇 |
1994年 | 2664篇 |
1993年 | 2633篇 |
1992年 | 2886篇 |
1991年 | 2875篇 |
1990年 | 2720篇 |
1989年 | 2684篇 |
1988年 | 2602篇 |
1987年 | 2511篇 |
1986年 | 2399篇 |
1985年 | 3092篇 |
1984年 | 3228篇 |
1983年 | 2698篇 |
1982年 | 3036篇 |
1981年 | 2761篇 |
1980年 | 2779篇 |
1979年 | 2821篇 |
1978年 | 3047篇 |
1977年 | 2967篇 |
1976年 | 2902篇 |
1975年 | 2798篇 |
1974年 | 2666篇 |
1973年 | 2846篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Jeroen J. L. M. Cornelissen W. Sander Graswinckel Alan E. Rowan Nico A. J. M. Sommerdijk Roeland J. M. Nolte 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1725-1736
The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003 相似文献
122.
M Lepère R Gobeille V.Malathy Devi M.A.H Smith B Aoaeh A.W Mantz 《Journal of Molecular Spectroscopy》2004,224(1):7-12
We have analyzed the methyl fluoride RQ(J,0)Q branch lines located near 1475 cm−1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 RQ(J,0) lines. 相似文献
123.
I. V. Denisova O. A. Ladyzhenskaya G. A. Seregin N. N. Uraltseva E. V. Frolova 《Journal of Mathematical Sciences》2005,130(4):4775-4779
Bibliography: 42 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 7–15. 相似文献
124.
M. Stangl V. Dittel J. Acker V. Hoffmann W. Gruner S. Strehle K. Wetzig 《Applied Surface Science》2005,252(1):158-161
At room temperature electroplated copper layers exhibit changes in resistivity, residual stress, and microstructure. This process, known as self-annealing, is intimately linked to the release of organic impurities, which stem from the incorporation of organic additives into the Cu layer in the course of the electroplating process. The behavior of these impurities during self-annealing, represented by the carbon content, could be detected by analytical radio frequency glow discharge optical emission spectrometry (GD-OES) and carrier gas hot extraction (CGHE). The precondition of a quantitative determination is a surface cleaning procedure to remove adsorbed organics from the copper surface. It was observed that at first almost all impurities have to leave the Cu metallization before an accelerated abnormal grain growth can start. The small amount of remaining organic species after self-annealing could be quantified by both examination techniques, GD-OES and CGHE. 相似文献
125.
W. Hampe 《Fresenius' Journal of Analytical Chemistry》1885,24(1):588-590
Ohne Zusammenfassung 相似文献
126.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
127.
A method has been developed for the determination of melengestrol acetate in bovine tissues at lower levels than previously reported. Liquid-liquid extraction of tissue homogenates provided crude clean-up while final isolation, screening, and quantification was done on-line with an automated, normal-phase, coupled-column high-performance liquid chromatographic system. The chromatographic system included phenyl and silica analytical columns for the purposes of isolation and final separation, respectively. These columns provided a large difference in selectivity when operated under normal-phase conditions which allowed for the efficient isolation of melengestrol acetate from the complex tissue extracts. Mobile phases were composed of hexane and dichloromethane modified with methanol and water. Transfer and enrichment of the analyte from the primary phenyl column to the silica column was via a short (12 mm x 4 mm I.D.) silica column. Regeneration and equilibration of the phenyl column was performed after the injection of each tissue extract and was accomplished simultaneously while analytical separation occurred on the final silica column. Routing of the mobile phases and regeneration solvent was performed with automated switching valves. The total time required for each analysis was 12 min. Quantification is demonstrated using external standards with UV detection at 287 nm. The overall recovery of the method was 86% with a coefficient of variation of 9.84% at the 10 ppb [the American billion (10(9] is used in this article] level in bovine liver extracts. 相似文献
128.
129.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported. 相似文献
130.
Basic principles of the generalized lattice model of multicomponent condensed systems are formulated. Short-range parts of interatomic interactions are taken into account by means of the geometric constraints method. Long-range parts of the interactions are taken into account in mean field approximation. The expression for Helmholtz free energy is obtained. A system of integral equations for the equilibrium distributions of components is derived. The asymptotic properties of its solutions are investigated. Moment expansion of interatomic interactions and localization of integral terms in free energy is obtained. A Ginzburg–Landau-like functional of free energy is derived. 相似文献